Question

A searchlight rotates through one complete revolution every 4 seconds. How long does it take the light to rotate through 90 degrees? Help me set it up please

Answer 1

1 full revolution=360
4seconds=360degrees
how many seconds is 90 degrees
4:360=x:90
4/360=x/90
simpllfiy
1/90=x/90
1=x

answer is 1 second

Answer 2

The ratio of the angle that the light rotate to the time in seconds should be equal. One revolution is equal to 360 degrees. Let x be the time it would take to rotate 90 degrees,
                               360 degrees / 4 seconds = 90 degrees / x seconds
The value of x is 1. Therefore, it would take only 1 second to rotate 90 degrees.